usr/src/cmd/lvm/metassist/layout/layout_device_cache.h

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  * Copyright 2003 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 #ifndef _LAYOUT_DEVICE_CACHE_H
  28 #define _LAYOUT_DEVICE_CACHE_H
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"
  31
  32 #ifdef __cplusplus
  33 extern "C" {
  34 #endif
  35
  36 /*
  37  * This module manages cached copies of a dm_descriptor_t's nvpair
  38  * list of attributes and its device name.  The caches are used to
  39  * make sure that the memory allocated to these objects is correctly
  40  * released after the layout process has finished.  The cached attrs
  41  * also allow the layout code to store and retrieve transient,
  42  * layout-private data in the same data structure as the other
  43  * relevant device information.
  44  *
  45  * There are two primary caches of information:
  46  *
  47  *    descriptor->name - which maps a dm_descriptor_t handle to
  48  *                      the associated device's name
  49  *
  50  *    name->attributes - which maps a device name to an nvlist_t
  51  *                      attribute collection.
  52  *
  53  * These two data structures thus allow the following lookup chain:
  54  *    descriptor->name->attributes.
  55  *
  56  * The attributes are accessed by device name because the it is the
  57  * unique identifier for the device.  The descriptor returned by
  58  * libdiskmgt is just an arbitrary handle, multiple calls into the
  59  * library may return different descriptors for the same device.
  60  *
  61  * Descriptors are also get re-cycled by the library which could
  62  * result in the same descriptor being used to represent different
  63  * devices (although not concurrently). To prevent such recycling
  64  * all of the descriptors are held until the layout process has
  65  * completed.
  66  *
  67  * Performance testing indicated that searching the lists of known
  68  * devices by display (CTD or DID) name or alias was a significant
  69  * bottleneck. A mapping from display name to descriptor was added
  70  * to address this.
  71  *
  72  * The module should be initialized once by calling create_device_caches()
  73  * prior to any call which accesses data maintained by the cache.
  74  *
  75  * The caches should be flushed after all accesses have completed by
  76  * calling release_device_caches.
  77  */
  78
  79 #include "libdiskmgt.h"
  80 #include "layout_device_util.h"
  81
  82 extern int      create_device_caches();
  83 extern int      release_device_caches();
  84
  85 extern int      add_cached_descriptor(char *name, dm_descriptor_t desc);
  86 extern dm_descriptor_t find_cached_descriptor(char *name);
  87
  88 extern int      add_cached_name(dm_descriptor_t desc, char *name);
  89 extern int      get_name(dm_descriptor_t desc, char **name);
  90
  91 extern int      add_cached_attributes(char *name, nvlist_t *attrs);
  92 extern int      get_cached_attributes(dm_descriptor_t desc, nvlist_t **list);
  93
  94 extern int      new_descriptor(dm_descriptor_t *desc);
  95 extern int      add_descriptors_to_free(dm_descriptor_t *desc_list);
  96
  97 #ifdef __cplusplus
  98 }
  99 #endif
 100
 101 #endif /* _LAYOUT_DEVICE_CACHE_H */